The present invention relates to a truck, in particular to a bulk goods dump truck of the so-called large dump truck type for the transport of mine overburden, raw materials and/or natural resources, having a chassis with wheels of which a plurality of wheels each have a single wheel drive and having a control device for the control of the speed and/or of the torque of the single wheel drives.
So-called large dump trucks such as are known from EP 1 359 032 A2 or from WO 92/04196 are primarily used in mining operations for the transport of the mined materials and ores. These bulk goods dump trucks are made in a size of several hundred metric tons unladen weight and working load so that special traction drives are required to control the corresponding enormous forces and drive conditions. In the large dump truck known from WO 92/04196, four wheels are combined in pairs at the rear axle and are mounted at two movably supported rocker arms at the vehicle frame. In this connection, a separate electric motor is associated with each of the wheels so that the wheels can also be driven individually at different speeds, in particular to prevent a grinding of the wheels during tight cornering. Optionally, a common single wheel drive can also be associated with a wheel pair so that, for example, two such single wheel drives are provided in the case of four wheels.
Such modern, diesel-electrically driven mining trucks must be able to transmit high traction forces with minimal wheel slip. Drive controls known from the automotive industry are not suitable here due to the special drive principle. When the large dump truck is operated in the ideal wheel slip range, this results in minimal tire wear and ideal driving stability since the transverse guidance properties of the tire are in the ideal range. It is required in this connection that a corresponding control is realized with a low sensor effort and works on different surfaces, also surfaces which change fast. A skid control which only limits the difference between driven wheels and non-driven wheels is therefore not sufficient or not possible.
Furthermore, with such large dump trucks, the braking process should take place solely controlled via the single wheel drives without the help of mechanical brakes. A mechanical braking system should only be used as a hand brake or emergency brake. Since such large dump trucks are, however, controlled via a torque set by the operator, braking to a standstill is not easily possible by the braking controlled by the single wheel drives since the single wheel drive braking torque is an active torque and not a reaction torque such as the friction torque of a mechanical brake. The driving torque of the single wheel drive must therefore be actively controlled to the load torque present when stationary. Older concepts make provision for this purpose for the torque limit of the brake torque to be limited to 0 Nm at a speed of zero. However, only a standstill on a straight surface is thus possible and influences of the mass acceleration are not taken into account so that a stop is only possible with the additional use of a mechanical brake and becomes very rough due to the non-considered environmental conditions.